Integrated circuit package system using heat slug

ABSTRACT

An integrated circuit package system includes a substrate having an integrated circuit die thereon; a heat slug having a tie bar, the tie bar having characteristics of singulation from an adjacent heat slug; and an encapsulant molded on the substrate, the heat slug, and the integrated circuit die includes the encapsulant which fills all of the space between the integrated circuit die and the heat slug.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of co-pending U.S. patent applicationSer. No. 11/279,131 filed Apr. 10, 2006, which claims the benefit ofU.S. Provisional Patent Application Ser. No. 60/669,585 filed Apr. 9,2005, and the subject matter thereof is hereby incorporated herein byreference thereto.

TECHNICAL FIELD

The present invention relates generally to methods and apparatus for thefabrication of integrated circuit packages, and more particularly tointegrated circuit package systems using heat slugs.

BACKGROUND ART

In the electronics industry, the continuing goal has been to reduce thesize of electronic devices such as camcorders and portable telephoneswhile increasing performance and speed. Integrated circuit packages forcomplex systems typically are comprised of a multiplicity ofinterconnected integrated circuit dies. The integrated circuit diesusually are made from a semiconductor material such as silicon orgallium arsenide. Semiconductor devices are formed in the various layersof the integrated circuit dies using photolithographic techniques. Theintegrated circuit dies may be mounted in packages that are then mountedon printed wiring boards.

Recently, there has been rapid development in semiconductor technologyand, as a result, semiconductors are becoming smaller, circuitry withinsemiconductors is becoming increasingly dense to provide higher speeds.As the density increases however, higher power is used in thesesemiconductor components. Higher power results in greater heatgeneration in such semiconductors. Thus, heat dissipation is becomingmore critical as semiconductor technology develops to address theincreasing demand for semiconductors having higher power and speed.

Various techniques may be used to remove or dissipate heat generated byan integrated circuit. One such technique involves the use of a mass ofconductive material. The mass of conductive material typically isreferred to as a heat slug. One of the primary purposes of a heat slugis to absorb and dissipate the heat generated by the electroniccircuitry on the integrated circuit and to spread the heat away from theintegrated circuit. The heat slug thereby removes the heat from theintegrated circuit and reduces the likelihood of the occurrence of hotspots that can have an adverse effect on the performance and reliabilityof the integrated circuit.

Heat slugs are made of a thermally conductive material such as aluminum,electro-plated copper, copper alloy, or ceramic, for example.

An electronic device may comprise at least one integrated circuitincluding a heat slug and a substrate carrier. Passive electroniccomponents such as capacitors also may be attached to the substratecarrier. Typically, the integrated circuit is attached to one side ofthe substrate carrier by means of a number of solder balls, solderbumps, or other alternative connections. The heat slug may be formed outof a suitable thermally conductive material such as copper, aluminum,carbon composites, or alternative suitable materials.

One problem with large heat slugs occurs during integrated circuitpackage sawing. While sawing a large heat slug, the saw blade can causesawing stress and heat slug burr.

Consequently, there still remains a need for improved, more economical,more efficient, and more readily manufactured and assembled heat slugs,heat slug package systems, and fabrication methods for use withintegrated circuit devices.

Solutions to these problems have been long sought but prior developmentshave not taught or suggested any solutions and, thus, solutions to theseproblems have long eluded those skilled in the art.

DISCLOSURE OF THE INVENTION

The present invention provides an integrated circuit package systemincluding: a substrate having an integrated circuit die thereon; a heatslug having a tie bar, the tie bar having characteristics of singulationfrom an adjacent heat slug; and an encapsulant molded on the substrate,the heat slug, and the integrated circuit die includes the encapsulantwhich fills all of the space between the integrated circuit die and theheat slug.

Certain embodiments of the invention have other advantages in additionto or in place of those mentioned above. The advantages will becomeapparent to those skilled in the art from a reading of the followingdetailed description when taken with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a heat slug matrix manufactured in accordancewith an embodiment of the present invention;

FIG. 2 is a cross-sectional view of FIG. 1 taken along line 2-2;

FIG. 3 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 4 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 5 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 6 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 7 is a cross-sectional view of an integrated circuit package systemmanufactured in accordance with an embodiment of the present invention;

FIG. 8 is a top plan view of the structure of FIG. 7;

FIG. 9 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 10 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 11 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 12 is an isometric view of a heat slug manufactured in accordancewith an embodiment of the present invention;

FIG. 13 is a cross-sectional view of an integrated circuit packagesystem manufactured in accordance with an embodiment of the presentinvention;

FIG. 14 is a top plan view of the structure of FIG. 13; and

FIG. 15 is a flow chart of an integrated circuit package system inaccordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following description, numerous specific details are given toprovide a thorough understanding of the invention. However, it will beapparent that the invention may be practiced without these specificdetails. In order to avoid obscuring the present invention, somewell-known system configurations, and process steps are not disclosed indetail.

Likewise, the drawings showing embodiments of the system aresemi-diagrammatic and not to scale and, particularly, some of thedimensions are for the clarity of presentation and are shown greatlyexaggerated in the FIGs. Also, where multiple embodiments are disclosedand described having some features in common, for clarity and ease ofillustration and description thereof, like features one to another willordinarily be described with like reference numerals.

The term “horizontal” as used herein is defined as a plane parallel tothe conventional plane or surface of the substrate, regardless of itsorientation. The term “vertical” refers to a direction perpendicular tothe horizontal as just defined. Terms, such as “on”, “above”, “below”,“bottom”, “top”, “side” (as in “sidewall”), “higher”, “lower”, “over”,and “under”, are defined with respect to the horizontal plane.

The term “processing” as used herein includes deposition of material orphotoresist, patterning, exposure, development, etching, cleaning,and/or removal of the material or photoresist as required in forming adescribed structure.

One method to improve thermal performance of an integrated circuitpackage is to use a heat slug having much higher thermal conductivitythan the epoxy molding compound (EMC) used around the integrated circuitdie. This type of integrated circuit package is often referred to as athermally enhanced semiconductor package.

A problem with large heat slugs is during a package sawing. Heat slugsawing with a blade can cause sawing stress and heat slug burr. Thus, ithas been discovered that a tie bar type heat slug in accordance withvarious aspects of the present invention will reduce the heat slugvolume that needs to be sawn. The tie bar type heat slug provides lowsawing stress, low burr and extends sawing blade life.

Referring now to FIG. 1, therein is shown a plan view of a heat slugmatrix 100 manufactured in accordance with an embodiment of the presentinvention. The heat slug matrix 100 includes a number of main bodyportions 102. The main body portions 102 are connected by a number oftie bars 104. The periphery of the heat slug matrix 100 has a rail 106connected to the tie bars 104 to form the heat slug matrix 100. The heatslug matrix 100 is formed of a thermally conductive material having arelatively high thermal conductivity as discussed below.

Referring now to FIG. 2, therein is shown a cross-sectional view of FIG.1 taken along line 2-2 after forming an array of semiconductor packages214. The array of semiconductor packages 214 is formed by providing asubstrate 200, such as a printed circuit board (PCB) or other suitablesubstrate material. Each of the number of integrated circuit dies 202 isattached to the substrate 200 using a suitable adhesive layer 204. Theintegrated circuit dies 202 are wire bonded to the substrate 200 using anumber of bond wires 206.

The heat slug matrix 100 is attached to the substrate 200 using a numberof supports 208. The number of supports 208 is formed on the substrate200, such as by using a suitable adhesive material. Typically, theheight of the supports 208 is greater than the height of the bond wires206 above the substrate 200. The heat slug matrix 100 is attached to thesupports 208. The supports 208 support the heat slug matrix 100 during amolding process that forms an encapsulant 210 to completely fill all ofthe space between the heat slug 102, of FIG. 1, and the integratedcircuit dies 202 leaving the top surface of the heat slug matrix 100exposed.

It has been discovered that the height of the supports 208 may beadequately controlled by using an adhesive having a low modulus ofelasticity and a high aspect ratio thereby reducing the possibility ofcrushing the supports 208 while attaching the heat slug matrix 100. Thesupports 208 can be formed by dotting the adhesive on the substrate 200.

A number of semiconductor package systems 214 is formed by a singulationprocess, such as sawing, along singulation lines 212 after theencapsulant 210 has adequately cured. It will be appreciated by thoseskilled in the art upon a reading of this disclosure that thesingulation occurs in the area of the tie bars 104 of the heat slugmatrix 100 shown in FIG. 1.

As discussed below with reference to FIGS. 3 through 6 and 9 through 12,the tie bars 104 have a reduced thickness compared to the main bodyportion 102. This provides less wear and tear on a saw blade, forexample, used in the singulation process. Additionally, the singulationprocess can be performed more quickly since less material needs to besawn.

The supports 208 are removed during the singulation process so nosupport is present in the semiconductor package systems 214.

Referring now to FIG. 3, therein is shown an isometric view of a heatslug 300 manufactured in accordance with an embodiment of the presentinvention. The heat slug 300 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 3 there are four tie bars 104 each centrally located alongone side of the main body portion 102. The tie bars 104 havesubstantially the same thickness as the main body portion 102 of theheat slug 300.

Referring now to FIG. 4, therein is shown an isometric view of a heatslug 400 manufactured in accordance with an embodiment of the presentinvention. The heat slug 400 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 4 there are four tie bars 104 each centrally located alongone side of the main body portion 102. The tie bars 104 have a thicknessequal to about half the thickness of the main body portion 102 of theheat slug 400 and are aligned with the lower surface of the main bodyportion 102. The thickness of the tie bars 104 is reduced by processingthe tie bars 104 and etching away the upper half of the tie bars 104,such as by using a half etch process.

Referring now to FIG. 5, therein is shown an isometric view of a heatslug 500 manufactured in accordance with an embodiment of the presentinvention. The heat slug 500 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 5 there are four tie bars 104 each centrally located alongone side of the main body portion 102. The tie bars 104 have a thicknessequal to about half the thickness of the main body portion 102 of theheat slug 500 and are aligned with the upper surface of the main bodyportion 102. The thickness of the tie bars 104 is reduced by processingthe tie bars 104 and etching away the lower half of the tie bars 104,such as by using a half etch process.

Referring now to FIG. 6, therein is shown an isometric view of a heatslug 600 manufactured in accordance with an embodiment of the presentinvention. The heat slug 600 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 6 there are four tie bars 104 each centrally located alongone side of the main body portion 102. The tie bars 104 have a thicknessequal to about half the thickness of the main body portion 102 of theheat slug 600 and are located in the middle portion of the sides of themain body portion 102. The thickness of the tie bars 104 is reduced byprocessing the tie bars 104 and etching away the upper and lowerportions of the tie bars 104, such as by using a half etch process.

Referring now to FIG. 7, therein is shown a cross-sectional view of anintegrated circuit package system 214 manufactured in accordance with anembodiment of the present invention. The integrated circuit packagesystem 214 includes the substrate 200. The substrate 200 typicallyincludes a number of upper contacts 704 formed on the upper surface ofthe substrate 200 and a number of lower contacts 706 formed on the lowersurface of the substrate 200. A number of vias 708 are formed throughthe substrate 200 to interconnect the upper contacts 704 and the lowercontacts 706 as needed for a particular design.

The integrated circuit die 202 is attached to the substrate 200 usingthe adhesive layer 204. The integrated circuit die 202 is electricallyconnected to the upper contacts 704 using the bond wires 206. Anysuitable wire bonding process, such as ultrasonic wire bonding, may beused to attach the bond wires 206 to the integrated circuit die 202 andthe upper contacts 704 on the substrate 200.

Referring now to FIG. 8, therein is shown a top plan view 800 of thestructure of FIG. 7. The main body portion 102 covers substantially theentire surface of the substrate 200 with the exception of the area ofthe substrate 200 over which the tie bars 104 extend.

It also has been discovered that adhesive crushing or solder maskcracking can be accepted as long as crushed adhesive particles andsolder mask cracking do not invade the final integrated circuit packagesystem 214 interior of the supports 208. Thus, in the embodiments of thepresent invention, the supports 208 are located out of the finalintegrated circuit package systems 214 into an area that is trimmedduring the package singulation or sawing process as discussed above.

It will be apparent to one skilled in the art upon a reading of thisdescription that the heat slugs 300, 400, 500, and 600 shown in FIGS. 3,4, 5, and 6 may be used to form the integrated circuit package system214.

Referring now to FIG. 9, therein is shown an isometric view of a heatslug 900 manufactured in accordance with an embodiment of the presentinvention. The heat slug 900 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 9 there are eight tie bars 104. A pair of the number of tiebars 104 is centrally located along each side of the main body portion102. The tie bars 104 have substantially the same thickness as the mainbody portion 102.

Referring now to FIG. 10, therein is shown an isometric view of a heatslug 1000 manufactured in accordance with an embodiment of the presentinvention. The heat slug 1000 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 10 there are eight tie bars 104. A pair of the plurality oftie bars 104 is centrally located along each side of the main bodyportion 102. The tie bars 104 have a thickness equal to about half thethickness of the main body portion 102 of the heat slug 1000 and arealigned with the lower surface of the main body portion 102. Thethickness of the tie bars 104 is reduced by processing the tie bars 104and etching away the upper half of the tie bars 104, such as by using ahalf etch process.

Referring now to FIG. 11, therein is shown an isometric view of a heatslug 1100 manufactured in accordance with an embodiment of the presentinvention. The heat slug 1100 includes the main body portion 102 and thenumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 11 there are eight tie bars 104. A pair of the plurality oftie bars 104 is located along each side of the main body portion 102.The tie bars 104 have a thickness equal to about half the thickness ofthe main body portion 102 of the heat slug 1100 and are aligned with theupper surface of the main body portion 102. The thickness of the tiebars 104 is reduced by processing the tie bars 104 and etching away thelower half of the tie bars 104, such as by using a half etch process.

Referring now to FIG. 12, therein is shown an isometric view of a heatslug 1200 manufactured in accordance with an embodiment of the presentinvention. The heat slug 1200 includes a main body portion 102 and anumber of tie bars 104 extending outwardly from the main body portion102. In FIG. 12 there are eight tie bars 104. A pair of the plurality oftie bars 104 is located along each side of the main body portion 102.The tie bars 104 have a thickness equal to about half the thickness ofthe main body portion 102 and are located in the middle portion of thesides of the main body portion 102. The thickness of the tie bars 104 isreduced by processing the tie bars 104 and etching away the upper andlower portions of the tie bars 104, such as by using a half etchprocess.

Referring now to FIG. 13, therein is shown a cross-sectional view of anintegrated circuit package system 214 manufactured in accordance with anembodiment of the present invention. The integrated circuit packagesystem 214 includes the substrate 200. The substrate 200 typicallyincludes a number of upper contacts 1304 formed on the upper surface ofthe substrate 200 and a number of lower contacts 1306 formed on thelower surface of the substrate 200. A number of vias 1308 is formedthrough the substrate 200 to interconnect the upper contacts 1304 andthe lower contacts 1306 as needed for a particular design.

The integrated circuit die 202 is attached to the substrate 200 usingthe adhesive layer 204. The integrated circuit die 202 is electricallyconnected to the upper contacts 1304 using the number of bond wires 206.Any suitable wire bonding process, such as ultrasonic wire bonding, maybe used to attach the bond wires 206 to the integrated circuit die 202and the upper contacts 1304 on the substrate 200.

Referring now to FIG. 14, therein is shown a top plan view of thestructure of FIG. 13. The main body portion 102 covers substantially theentire surface of the substrate 200 with the exception of the area ofthe substrate over which the tie bars 104 extend.

It will be apparent to one skilled in the art upon a reading of thisdescription that the heat slugs 900, 1000, 1100, and 1200 shown in FIGS.9, 10, 11, and 12 also may be used to form the integrated circuitpackage system 214.

Additionally, the number of tie bars 104 may be increased if additionalsupport for the heat slug matrix 100 is needed in a particularintegrated circuit package system. Also, it has been discovered that theintegrated circuit package system of the present invention is compatiblewith both lead frame ball grid array (LFBGA) and quad flat packnon-leaded (QFN) integrated circuit packages.

The heat slug used for this invention is flat and has no supports thatattach to the substrate in the integrated circuit package systems 214. Amajor advantage of using a flat heat slug is better thermal performancein comparison with conventional heat slugs that have supports because ofincreased exposed heat slug area.

Referring now to FIG. 15, therein is shown a flow chart of an integratedcircuit package system 1500 in accordance with the present invention.The integrated circuit package system 1500 includes providing asubstrate having an integrated circuit die thereon in a block 1502;providing a support on the substrate in a block 1504; positioning a heatslug having a tie bar by the tie bar on the support in a block 1506;encapsulating the substrate and the integrated circuit with anencapsulant, the encapsulant in contact with the heat slug in a block1508; and singulating the substrate, heat slug, and encapsulant toremove the support in a block 1510.

Thus, it has been discovered that the integrated circuit package systemof the present invention furnishes important and heretofore unavailablesolutions, capabilities, and functional advantages for packagingintegrated circuits. The resulting process and configurations arestraightforward, economical, uncomplicated, highly versatile andeffective, use conventional technologies, and are thus readily suitedfor manufacturing integrated circuit devices that are fully compatiblewith conventional manufacturing processes and technologies.

While the invention has been described in conjunction with a specificbest mode, it is to be understood that many alternatives, modifications,and variations will be apparent to those skilled in the art in light ofthe aforegoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications, and variations which fall within thescope of the included claims. All matters hithertofore set forth hereinor shown in the accompanying drawings are to be interpreted in anillustrative and non-limiting sense.

1. An integrated circuit package system comprising: a substrate havingan integrated circuit die thereon; a heat slug having a tie bar, the tiebar having characteristics of singulation from an adjacent heat slug;and an encapsulant molded on the substrate, the heat slug, and theintegrated circuit die includes the encapsulant which fills all of thespace between the integrated circuit die and the heat slug.
 2. Theintegrated circuit package system as claimed in claim 1, wherein theheat slug, further comprises: a main body portion and a tie barsubstantially centrally located along each side of the main bodyportion.
 3. The integrated circuit package system as claimed in claim 1,wherein the heat slug, further comprises: a heat slug having a main bodyportion and a tie bar having a thickness of greater than about half thethickness of the main body portion.
 4. The integrated circuit packagesystem as claimed in claim 1, wherein the heat slug, further comprises:upper and lower surfaces; and a tie bar located at least one of flushwith the upper surface of the heat slug, flush with the lower surface ofthe heat slug, and intermediate the upper and lower surfaces of the heatslug.
 5. The integrated circuit package system as claimed in claim 1,wherein the heat slug, further comprises: a main body portion and a pairof tie bars located along each side of the main body portion.
 6. Theintegrated circuit package system as claimed in claim 1, furthercomprising: a plurality of contacts on the substrate; wires bonding theintegrated circuit die to the contacts; a heat slug having a pluralityof tie bars; and an encapsulant encapsulating the substrate and theintegrated circuit with an encapsulant, the encapsulant in contact withthe heat slug.
 7. The integrated circuit package system as claimed inclaim 6, wherein the heat slug, further comprises: a main body portion;wherein: each of the plurality of tie bars is substantially centrallylocated along each side of the main body portion.
 8. The integratedcircuit package system as claimed in claim 6, wherein the heat slug,further comprises: a main body portion; and the plurality of tie barshaving a thickness of greater than about half the thickness of the mainbody portion.
 9. The integrated circuit package system as claimed inclaim 6, wherein the heat slug, further comprises: upper and lowersurfaces; and wherein: the plurality of tie bars is located at least oneof flush with the upper surface of the heat slug, flush with the lowersurface of the heat slug, and intermediate the upper and lower surfacesof the heat slug.
 10. The integrated circuit package system as claimedin claim 6, wherein the heat slug, further comprises: a main bodyportion and a pair of tie bars located along each side of the main bodyportion.